Double wall bags

ABSTRACT

The invention relates to plastic bags and sack for use especially in the food and pharmaceutical industries. The bag ( 2 ) comprises inner and outer bag sections ( 4, 14 ) which are joined at least at an upper portion in a manner which allows them to be separated when required, such as by heat sealing. The outer bag section ( 14 ) may be provided with a mouth ( 10 ) through which the inner bag section can be withdrawn when required. Alternatively, the outer bag section may be peeled away from the inner bag section. The inner bag section is heat sealed after filling with contents to retain the contents in the inner portion. The heat sealing step also serves to secure the bag sections together as above. The inner bag section is preferably provided with a closeable mouth ( 132 ) separate from the end by which it is filled, through which the contents may be dispensed.

The present invention relates to bags and sacks and in particular toplastic bags and sacks for use in the food and pharmaceuticalindustries, especially for the storage and transport of powdery orgranular materials, other flowable solid materials or the like.

The food and pharmaceutical industries necessarily place stringentrequirements on the handling of ingredients and components, as well ason final products sold to commercial users and consumers. Theserequirements are essential to prevent contamination with dust, dirt orother foreign bodies, or with, for example, bacteria. Conventional bagsand sacks have tended to use at least one layer, usually an outer layer,of a paper-based material which is closed by stitching. This sort ofconstruction has the significant disadvantage that, on opening of thebag, pieces of paper or stitching thread may contact and become mixedwith the contents of the bag. Other bags are made of plastics materialand suffer a similar problem in that the closure of the bag oftenrequires the bag to be cut open to access the contents. This carries thedanger that shards of plastic from the cutting step can contact the bagcontents.

The present invention seeks to overcome these problems by providing aplastic bag or sack with an easy open closure which does not require anycutting and which does not generate any loose pieces or shards ofplastic or other material on opening. The present invention furtherseeks to provide a plastic bag or sack wherein the portion of the bagcontaining product is maintained in a clean, hygienic environment—forexample during transport and storage—until the bag is to be opened. Morespecifically, the present invention provides a bag comprising an innerbag portion and an outer cover portion, both portions being closeableafter the inner portion is filled with contents and the inner bagportion being removable or separable from the outer portion withoutdisrupting the closure of the inner bag portion.

According to a first aspect of the present invention there is provided aplastic bag comprising:

-   -   i) a cover section comprising first and second opposed walls;    -   ii) a bag section comprising third and fourth opposed walls        joined at their side and base edges and an open end by means of        which the bag section may be filled with contents, the first and        second walls being arranged to enclose the bag section;    -   iii) a closeable mouth defined in a wall of the bag section for        access in use to the interior of the bag section;    -   iv) a closeable region, distinct from the mouth, including an        end portion of the cover section and an end portion of the bag        section proximate the open end of the bag section, within which        closeable region the bag section may be sealed closed after        filling;        -   wherein, in the closeable region, an internal face of at            least one of the respective first and second walls is            attached and/or attachable to an adjacent external face of a            wall of the bag section, the attachment being such that the            bag section is separable in use from the cover section            without compromising the seal of the bag section in the            closeable region.

Preferably the open end of the bag section may operatively be sealedafter filling by heat sealing the bag section walls together in thecloseable region.

In a preferred embodiment of the invention, for attachment of the coversection to the bag section in said closeable region, an internal face ofat least one of the respective first and second walls of the coversection is attachable to at least one external face of a bag sectionwall by heat sealing in the closeable region. Preferably this heatsealing is effected in the same operation by which the bag section wallsare sealed together In the closeable region.

Preferably at least one member selected from the group comprising theinternal faces of the first and second walls and the respective externalfaces of the bag section walls comprises a first treated area in thecloseable region, said first treated area being effective to limit thestrength of the heat seal between the cover section and bag section.Thus at least one of the walls of the cover section and/or of the bagsection includes such a first treated area, whereby the resultingstrength of the heat seal is insufficient to prevent intentionalseparation of the bag section from the cover section by a user. The heatseal is, nevertheless strong enough to maintain the union between thecover section and the bag section in the closeable region untilseparation of the respective sections is desired.

In a particularly preferred embodiment said first treated area comprisescoated or printed areas, zones or regions (hereinafter “printed areas”),the printed areas being resistant to heat sealing. Thus little or noheat seal is formed within the printed areas, but a heat seal is formedoutside the printed areas, the result being a weaker heat seal acrossthe treated area taken as a whole.

In a preferred variation of the bag of the invention the first andsecond walls are also separably attached respectively to the bag sectionwalls in areas other than said closeable region. Preferably in thisvariation the first and second walls are substantially co-extensive withthe width of the bag section walls. The width of the cover section wallsshould not be less than that of the bag section walls, but may be more.Most preferably, the first and second walls are separably attached tothe bag section walls in areas proximate the side edges of the bagsection.

Preferably in this variation the first and second walls are removeablyheat sealed respectively to the bag section walls in said separablyattached areas.

More preferably in this variation at least one of the first wall and theadjacent bag section wall and/or at least one of the second wall and theadjacent bag section wall comprises a second treated area, said secondtreated area being effective to limit the strength of the heat sealbetween respectively the first and third and the second and fourth wallsin said separably attached areas. Preferably said second treated areacomprises printed areas, the printed areas being resistant to heatsealing.

The first and/or second treated areas may comprise, in a said treatedarea, alternate printed and non printed areas. The relative areas of theprinted and non printed areas can be determined by one skilled in theart by simple experiment in order to achieve a union between the wallsof appropriate strength, allowing the walls to be separated whendesired. This may depend, for example, on the materials from which thewalls are made and the characteristics of the particular heat sealingapparatus which is used. Preferably, however, the area of the printedareas is greater than the area of the non-printed areas.

In a particularly preferred arrangement, the printed and non-printedareas alternate to define stripes across the closeable region and/oracross the separably attached areas. In preferred examples, typicallythe non-printed areas have a width of not more than about 2 mm,preferably about 0.5 mm to 1.5 mm and typically the printed areas have awidth of not more than about 10 mm, preferably about 3 mm to about 8 mm,more especially about 5 mm.

In a particularly preferred form of the invention, the whole surface ofa wall comprises with a treated area. For example the whole innersurface of the first and/or may comprise a treated area. Likewise, thewhole external surface of the third and/or fourth walls may comprise atreated area. The external surface of the first and second closure flaps(where present) may also comprise a treated area. In the most preferredarrangement, the whole of the inner surface of the first and secondwalls comprises a treated area, the surfaces of the third and fourthwalls not being coated or printed and, where present the surfaces of theclosure flap(s) not being treated. It is especially preferred that thewhole inner surfaces of the first and second walls are printed orotherwise coated with alternating printed and non printed areas in apattern of stripes as described in the preceding paragraph.

In an alternative (or additional) arrangement, the treated area maycomprise an embossed area of one or more of the walls.

In another preferred form of the invention the cover section is longerthan the bag section such that the cover section extends beyond the base(lower) end of the bag section, the first and second walls being joinedto each other in said lengthwise extending portion. For example, in thelengthwise extending portion, the first and second walls may be joinedto one another by a permanent or separable heat seal at the edges ofsaid walls.

In one alternative preferred arrangement the width of the cover sectionis greater than the width of the bag section such that the cover sectionextends beyond the side edges of the bag section, the first and secondwalls being joined to each other in said widthwise extending portion.For example, in the widthwise extending portion, the first and secondwalls may be joined to one another by a permanent or separable heat sealat the edges of said walls. Preferably, but not essentially, in thisarrangement the first and second walls are not attached respectively tothe bag section walls in areas other than said closeable region.

In a particularly preferred embodiment the plastic bag of the inventionfurther comprises:

-   -   a first closure flap overlying and closing said mouth defined in        a wall of said bag section, said first closure flap including a        first attached region which is peelably attached to said bag        section wall such that at least a portion of said first closure        flap may be peeled away from said bag section wall across the        peelably attached region to reveal the mouth, and, optionally, a        second attached region spaced from the peelably attached region        in which second region said first closure flap is also attached        to said bag section wall.

In an alternative, but functionally substantially equivalent, embodimentthe plastic bag of the invention further comprises:

-   -   a first closure flap overlying and closing said mouth defined in        a wall of said bag section and including a first region which is        attached to a said bag section wall, said first closure flap        including at least one line of weakness defining a tearable        portion of said first closure flap within which tearable portion        said first closure flap is not attached to the bag section wall        and which tearable portion can be opened by tearing along the        line of weakness to reveal the mouth; and, optionally, a second        attached region spaced from the tearable portion in which second        region said first closure flap is also attached to said bag        section wall.

Preferably in these embodiments the first closure flap extends into thecloseable region. In this case a first treated area may be formed on thefirst closure flap instead of a treated area of the bag section. Thatis, a first treated area on an external face of a bag section wall isthen no longer required and is provided instead on the first closureflap. In one variation, the wall of the bag section to which the closureflap is attached may be made shorter than the other wall of the bagsection, the closure flap then acting as an extension of the bag sectionwall to which it is attached.

In another embodiment of the invention one or both of the respectivefirst and second walls of the cover section is/are adhered to the bagsection proximate the open end of the bag section. This may be inaddition to the heat sealing in the closeable region as defined above.Preferably in this case the cover section is adhered to the bag sectionat marginal portions of the closeable region.

In another embodiment of the invention, the plastic bag furthercomprises a second closeable mouth defined in the first or second wallof the cover section for access in use to the bag section. Thisembodiment is applicable both to the case where the cover sectionextends widthwise beyond the bag section (more especially where theedges of the first and second walls in the widthwise extending portionare permanently joined together, so that the bag section can then bewithdrawn from the cover section through the second closeable mouth) andto the case where the cover section and the bag section have nominallythe same width.

In a preferred variation of this embodiment, the plastic bag furthercomprises:

-   -   a second closure flap including a first attached region which is        peelably attached to said cover section wall such that at least        a portion of the closure flap may be peeled away from said cover        section wall across the peelably attached region and a second        attached region spaced from the peelably attached region in        which second region the second closure flap Is also attached to        said cover section wall.

In an alternative, but substantially functionally equivalent variation,the plastic bag further comprises:

-   -   a second closure flap including a first region which is attached        to said cover section wall, the second closure flap including at        least one line of weakness defining a tearable portion of the        closure flap within which tearable portion the closure flap is        not attached to said cover section wall and which tearable        portion can be opened by tearing along the line of weakness and        a second attached region spaced from the tearable portion in        which second region the second closure flap is also attached to        said cover section wall.

Where the plastic bag further comprises a second closeable mouth definedin the first or second wall of the cover section for access in use tothe bag section, the second closure flap (in either of the abovealternative constructions) is arranged to cover the mouth so that whenthe second closure flap is peeled or torn back, the mouth is revealed.

As an alternative to, or in addition to, the second closure flap theplastic bag may preferably comprise gripping means formed in or on, orattached to the first or second walls, to facilitate gripping of saidwalls on separation of the cover section from the bag section.

According to a second aspect of the invention there is provided a methodof handling a flowable product comprising:

-   -   i) providing a bag according to the first aspect of the        invention;    -   ii) filling the bag section with the flowable product through        the open end of the bag; and    -   iii) applying heat sealing means to the closeable region thereby        to heat seal the bag section walls together to sealingly close        the bag section and to heat seal the first and/or second walls        to the bag section walls to separably attach the cover section        and bag section together.

Preferably the method further comprises:

-   -   iv) separating the cover section from the bag section in the        closeable region;    -   v) if necessary, separating the cover section from the bag        section outside the closeable region and    -   vi) withdrawing the bag section from the cover section.

According to a third aspect of the invention there is provided a plasticbag comprising:

-   -   i) a cover section comprising first and second opposed walls;    -   ii) a product containing bag section comprising third and fourth        opposed walls joined at their side and base edges, the first and        second walls being arranged to enclose the bag section;    -   iii) a closeable mouth defined in a wall of the bag section for        access in use to the interior of the bag section;    -   iv) a sealing region, distinct from the mouth, including an end        portion of the cover section and an end portion of the bag        section within which sealing region the bag section is sealed        closed after filling bag section with product;        -   wherein, in the sealing region, an internal face of at least            one of the respective first and second walls is attached to            an adjacent external face of a wall of the bag section, the            attachment being such that the bag section is separable in            use from the cover section without compromising the seal of            the bag section in the sealing region.

Preferably, within the sealing region, the respective first and secondwalls of the cover section are attached to at least one of the externalfaces of the respective bag section walls of the bag section by means ofa heat seal formed contemporaneously with the heat seal which seals thebag section walls.

Preferably at least one of the Internal faces of the first and secondwalls and the external faces of the bag section walls comprises atreated area in the sealing region, the treated area being effective tolimit the strength of the heat seal between the cover section and bagsection.

In a preferred embodiment of this aspect of the invention, the plasticbag further comprises:

-   -   a first closure flap overlying and closing said mouth defined in        a wall of said bag section, said first closure flap including a        first attached region which is peelably attached to said bag        section wall such that at least a portion of said first closure        flap may be peeled away from said bag section wall across the        peelably attached region to reveal the mouth, and, optionally, a        second attached region spaced from the peelably attached region        in which second region said first closure flap is also attached        to said bag section wall.

In an alternative, but functionally substantially equivalent embodimentof this aspect of the invention, the plastic bag comprises

-   -   a first closure flap overlying and closing said mouth defined in        a wall of said bag section said first closure flap including a        first region which is attached to a said bag section wall, said        first closure flap including at least one line of weakness        defining a tearable portion of said first closure flap within        which tearable portion said first closure flap is not attached        to the bag section wall and which tearable portion can be opened        by tearing along the line of weakness to reveal the mouth; and,        optionally, a second attached region spaced from the tearable        portion in which second region said first closure flap is also        attached to said bag section wall.

In a preferred variation the first closure flap extends into thecloseable region. Preferably in this variation a first treated area isformed on the first closure flap instead of a treated area of the bagsection. More preferably, a treated area is provided across the whole ofone or both of the first and second walls and, preferably, no treatedarea is provided on the bag section.

For a better understanding of the invention and to show how the same maybe carried into effect reference will be made, by way of example only,to the following drawings, in which:

FIG. 1 is a partially cut away plan view of a bag according to oneembodiment of the invention;

FIG. 2A is a cross-section along the line II-II of FIG. 1;

FIG. 2B is similar to FIG. 2A showing a variation in the construction ofa closure flap;

FIG. 3 is a partially cut away plan view of the bag of FIG. 1 from thereverse side;

FIG. 4 is a simplified plan view of an alternative construction of aclosure flap of the bag of the invention;

FIG. 5 is a representation of treated and non-treated areas on a coversection or bag section wall of the invention;

FIG. 6 is a partially cut away plan view of a bag according to a secondembodiment of the invention;

FIG. 7 is a cross-section along line VII-VII of FIG. 6; and

FIG. 8 is similar to FIG. 7, showing a further closure flap on theexterior of the bag.

Referring now to the FIGS. 1 to 4, the bag 2 of the this embodimentcomprises a cover section 4 defined by first and second opposed walls10, 12 and a bag section 14 defined by third and fourth opposed walls16, 18. The bag section 14 is smaller than the cover section 4 and lieswithin the cover section 4. The cover section 4 is closed on opposedside edges 20 and lower (base) end edge 22 by suitable means for joiningthe first and second walls together, such as adhesive or, morepreferably, heat welding or heat sealing. The opposed side edges 20 maybe joined together in a permanent or (preferably) separable manner. Thebag section 14 is closed on opposed side edges 24 and lower (base) endedge 26 by suitable means for joining the third and fourth wallstogether. Alternatively, the respective first and second walls and thirdand fourth walls may be formed integrally, as a flattened tube. At end28 the first and second walls 10, 12 are not joined to each other. Thethird and fourth walls 16, 18 define an open end of the bag 30, thewalls 16, 18 also not being joined to each other at this end. In FIGS. 1to 3, the ends 28, 30 are shown slightly displaced from one another, forclarity of illustration. Preferably, however, the ends 28, 30 lieessentially along the same notional line.

First wall 10 includes a mouth 32 which preferably takes the form of aslit formed in the first wall 10. The mouth 32 may initially be in theform of a line of weakness, such as a line of perforations, which isbreached when required to form the mouth 32. Most preferably, a closureflap 34 is provided on the first wall 10. The closure flap 34 extendsacross substantially the whole width of first wall 10 and so lies over,and closes, the mouth 32. The closure flap 34 is affixed to the firstwall 10 in region 36 preferably by a suitable adhesive. The adhesive maybe permanent so that the closure flap 34 and the first wall are notseparable in region 36. The closure flap 34 is also attached to thefirst wall 10 in region 38. Region 38 is such that the closure flap 34may be peeled away from the first wall 10 across the region 38 withoutsubstantially or significantly damaging the first wall 10. Moreespecially, it is important that the bond in the region 38 (whetheradhesive or otherwise) between the closure flap 34 and the first wall 10is such that the first wall 10 and the closure flap 34 can be separatedfrom one another without generating shards or pieces of plastic whichmay subsequently contaminate, or have the potential to contaminate, thecontents of the bag section 4. Region 38 may be a welded or heat sealedregion but is most preferably at least one region of peelable adhesive.It Is most preferable that the region 38 extends from one side edge 20to the other side edge 20 without interruption. In the illustratedembodiment, region 38 comprises a single line of peelable adhesive. Inalternative constructions, a plurality, especially two or three, linesof peelable adhesive may be provided. A corresponding region of peelableadhesive (not illustrated) may be provided on the opposite side of themouth 32 from region 38. A line of weakness 40 is provided at one sideof the closure flap 34 and a corresponding line of weakness (notillustrated) is provided at the other side of the closure flap. Foraccess to the mouth 32, the closure flap 34 is torn along the lines ofweakness 40 and peeled back through the region 38 to reveal the mouth32. Numerous alternative constructions for the lines of weakness 40 arepossible. For example, the lines of weakness could be curved or at anangle with respect to the side edges 20, or a single line of weakness 40in the form of an arc extending from the leading edge 34 a of theclosure flap 34 above the region 38 and the mouth 32 and returning tothe leading edge 34 a at the other side of the closure flap 34.

Where the first and second walls are separably (rather than permanently)attached to one another, or separably attached to the bag section, theclosure flap may be omitted and, if the closure flaps 34 is present, themouth 32 may be omitted. In preferred variations, both the closure flap34 and mouth 32 are present.

In some preferred constructions of the bags according to this embodimentof the invention, the bag section 14 is initially attached (e.g.adhered) to the cover section 4 with an adhesion sufficient to maintainthe desired relative positions of the sections 4, 14 prior to the heatsealing step described below by which the bag section is joined to thecover section in the closeable region. This adhesion, if present, mustbe sufficient to maintain the relative positions of the bag section 14and cover section 4, but not sufficient to prevent easy separation ofthe sections 4, 14 when required. Thus, for example, an external face ofthe third wall 16 may be provided with a line of adhesive adjacent theopen end 30 by means of which the third wall is adhered to an internalface of the first wall 10. Similarly, an external face of the fourthwall 18 may be provided with a line of adhesive adjacent the open end 30by means of which the fourth wall 18 is adhered to an internal face ofthe second wall 12.

The bags of this embodiment of the invention are provided with acloseable region 42 which can extend from above the mouth 32 towards theends 28, 30 of the cover section and bag section 4, 14. The actualextent of the closeable region 42 can be determined in accordance withthe manufacturer's wishes but it is essential in this embodiment thatthe closeable region 42 does not encompass the mouth 32. Within thecloseable region, heat sealing means can be applied to the bag wherebythe internal faces of the third and fourth walls 16, 18 are heat sealedtogether. In this way the bag section 14 is sealed and closed afterhaving been filled with contents. This heat sealing step may also sealtogether any portions of the first and second walls 10, 12 which extendbeyond the upper edge of the bag section 14.

The heat sealing step for sealing together the third and fourth walls16, 18 is also effective in securely attaching the cover section 4 tothe bag section 14. This is achieved in accordance with the invention insuch a way that the sections 4, 14 are sufficiently securely attached toprevent them from being separated in normal transport and handling butnot so securely that the sections 4, 14 cannot be separated manuallywhen desired.

It would normally be expected that simple application of a heat sealwhich joins the first wall 10 to the third wall 16 and the second wall12 to the fourth wall 18 will result in a joint between the respectivewalls of a strength such that the cover portion 4 is not easilyseparable when required from the bag section 14. In this respect, thechoice of materials for the first, second, third and fourth walls 10,12, 16, 18 can affect the strength of the heat seal and it is possible,for example, to achieve a heat seal of the desired strength by selectingmaterials respectively for the first and third and for the second andfourth walls whose compatibility for heat sealing is poor. In this way,the strength of the resultant heat seal is not too great and so thecover section 4 can be separated from the bag section 14 when required.The choice of materials in this respect is within the skill andknowledge of the person skilled in the art.

However, in preferred embodiments of the invention, at least one of thefirst, second, third and fourth walls, 10, 12, 16, 18 is provided, atleast in the closeable region, with a treated area 44 which interfereswith the heat seal so limiting or reducing its strength to an extentthat the first and bag sections 4, 14 can be separated when required.The treated area 44 is preferably provided on an internal surface ofboth the first and second walls 10, 12 or on an external surface facingthe internal surface of the walls 10, 12, such as both external surfacesof the third and fourth walls 16, 18.

The treated area 44 can take any reasonable form for appropriatelyweakening the heat seal in the closeable region (that is, the heat sealother than that between the internal surfaces of the third and fourthwalls) provided that other features of the bag are not adverselyaffected. For example, the first and second walls 10, 12 or the thirdand fourth walls 16, 18 may be provided with an embossed region whichinterferes with the heat seal.

In a particularly preferred form of the invention the treated areaextends over the whole of the internal surfaces of the first and secondwalls 10,12. Of course, the effect of the treated area is apparent onlyin those areas which are subsequently heat sealed.

Most preferably, however, the treated area 44 is a coated or printedarea. The treated area 44 is preferably not printed across the wholearea. Rather, the treated area preferably comprises printed regions 44Aand non-printed regions 44B (FIG. 5). The relative areas of the printedand non-printed regions will determine the strength of the resultantheat seal, that is, in general terms, the greater the area of theprinted regions, the weaker will be the heat seal. Preferably, thetreated area comprises alternate printed and non-printed regions, forexample in the form of alternating stripes which may be arranged, forexample, diagonally with respect to side edges 20. The relative areas ofthe printed and non-printed regions in any given bag of the inventioncan be determined by simple experiment by the person of ordinary skillin the art, in order to achieve an effective bond strength of the heatseal. Typically, relatively wide printed regions will alternate in thetreated area 44 with relatively narrow non-printed regions.

In use of the bags according to the invention, the bag section 14 isfirst filled with the product to be contained in the bag 2 through theopen end 30. When the desired amount of product has been placed in thebag section 14, the bag is closed by heat sealing in the closeableregion 42. That is, the heat sealing In the closeable region 42 sealstogether the third and fourth walls 16, 18 whereby the product is sealedwithin, and prevented from escaping from, the bag section 14. In thesame sealing step, the cover section and bag section 4, 14 are joinedtogether with a heat seal, in the closeable region 42, between theinternal surfaces of the first and second walls 10, 12 and externalsurfaces of the bag section 14. It is noted that this heat sealing maybe in addition to an initial adhesion of the cover section 4 and bagsection 14 sufficient to retain the sections together before and duringfilling. The heat sealing in the closeable region 42 may, for example,form a joint between the first and third walls 10, 16 and the second andfourth walls 12, 16. After the heat sealing step, the bag and itscontents may be stored or transported as required. When access isrequired to the contents of the bag, the mouth 32 in the first wall 10is opened. In accordance with the illustrated embodiment, the closureflap 34 is peeled back through the region 38 by tearing along the linesof weakness 40 to reveal the mouth 32. The cover section 4 and bagsection 14 are then separated by breaking apart the heat seal in thecloseable region 42 (which includes a treated area 44) between thesections 4, 14. The bag section 14 may then be withdrawn through themouth 32 of the cover section 4. Alternatively, depending on the extentof the provision of the treated area(s) 44, the first and second wallsmay simply be peeled away from the bag section 14. At this stage, theheat seal between the third and fourth walls of the bag section remainsintact so that the contents continue to be retained in the bag section14. The bag section 14 may then be opened as desired to access thecontents.

In a much preferred embodiment the bag section 14 is also provided witha mouth 132 and a closure flap 134 overlying and closing the mouth 132.The construction of the closure flap 134 is essentially the same as thatof the closure flap 34. Thus, the closure flap 134 is preferablypermanently adhered to the bag section 14 in region 136 and is peelablyadhered to the bag section 14 in region 138. The closure flap 134 isalso provided with lines of weakness 140. Thus, after separation of thecover section 4 and the bag section 14, such as by extraction of the bagsection 14 from the cover section 4 through mouth 32, the bag section 14can be opened by tearing the closure flap 134 along the lines ofweakness 140 and peeling back through the peelably attached region 138to reveal the mouth 132, through which the contents of the bag section14 may be dispensed. As with the mouth 32, the mouth 132 may initiallybe formed as a line of weakness such as a perforation which is breachedto form the open mouth 132.

The closure flap 134 and mouth 132 may preferably be disposed on thefourth wall of the bag section, that is so that the closure flap 134 andmouth 132 are arranged on the wall (18) of the bag section which isdistant from the mouth 32 and closure flap 34. In this construction, atreated area 144 may be formed on a region of the closure flap 134 onits face juxtaposed with the second wall 12. Such a treated area 144 onthe closure flap 134 is preferably in addition to the treated area 44formed on the third wall 16 in juxtaposition to the first wall 10.However, a treated area on the closure flap 134 is not needed if theinternal surface of the second wall 12 has a corresponding treated area44.

As can be seen from FIG. 2A, the closeable region in one preferredconstruction of the bag according to this embodiment of the inventionencompasses the third and fourth walls 16, 18, the first and secondwalls 10, 12 and the first and second closure flaps 34, 134.

FIGS. 2A, 2B and 3 illustrate the mouth 132 and closure flap 134 at thetop portion of the bag, approximately adjacent the open end 30. Thisconstruction is preferred but not essential. The mouth 132 may be formedin any part of the third or fourth wall 16, 18 other than the closeableregion, and the closure flap 134 is positioned accordingly on the thirdor fourth wall 16, 18 so that the mouth 132 is closed. In theseconstructions, the closure flap 134 may be placed entirely outside thecloseable region 42.

In a preferred construction, as shown in FIG. 2B, the fourth wall 18 ismade shorter than the third wall 16 so that the mouth 132 is defined byan upper end edge of the fourth wall 18. The closure flap is thenpeelably attached to the fourth wall 18 in region 138 only with theremainder of the closure flap 134 directly overlying the internal faceof the third wall 16. In effect, the upper portion of the closure flapbecomes an extension of the fourth wall 18. Permanently attached region136 is omitted. In this construction the heat seal which closes the bagsection to retain the contents therein is made between the third wall 16and the closure flap 134, but not with any part of the fourth wall 18.References herein to forming a heat seal between the third and fourthwalls 16, 18 should be construed accordingly to include thisconstruction, unless the context specifically requires otherwise.Likewise in this construction there is no heat seal in the closeableregion 42 between the second and fourth walls 12, 18. Since the closureflap 134 acts as an extension of the fourth wall 18, the union in thecloseable region is between an inner face of the second wall 18 and anexternal face of the closure flap 134. Again, reference to a union (heatseal etc) between an inner face of the first or second wall and anexternal face of a bag section wall should be construed to include theoption of a closure flap of the bag section acting as an extension ofthe relevant bag section wall.

A similar construction is possible with respect to the closure flap 34and the first wall 10 in that the first wall 10 may be made shorter thanthe second wall 12 so that the closure flap 34 is adhered to the firstwall 10 only in region 38 with the upper part of the closure flap 34directly overlying the third wall 16. The upper part of the closure flap34 then acts in effect as an extension of the first wall 10 and is heatsealed in use to the treated area 44 on the third wall 16, in thecloseable region 42. References to portions of the first wall in thecloseable region and/or the interaction of the first wall with thetreated area should be construed accordingly.

FIG. 4 illustrates an alternative construction of the closure flap whichmay be applied to either of the closure flaps 34 and 134 (and to closureflaps 334 and 434 described below). This construction achieves the sameresult as the construction illustrated in FIGS. 1 to 3 but does notrequire a peelable adhesive. In the construction of FIG. 4 the closureflap 234 includes a line of weakness 240 extending in a curved line oneither side of the mouth 232. Other lines of weakness are possible suchas “V” or “U” shapes. An area 200 is thus bounded by the line ofweakness 240 and within this area the closure flap 234 is not adhered atall to the underlying wall (10, 12, 16 or 18). Outside the area 200, inarea 202 the closure flap 234 is adhered, welded or otherwise bonded tothe underlying wall to form a closure over the mouth 232. To this end,heat sealing or adhering of the closure flap 234 around its marginaledges is shown at 204 in FIG. 4. The relevant bag section 4, 14 may thusbe opened by tearing the closure flap 234 along the line of weakness 240to reveal the mouth 232.

Referring now to FIGS. 6 to 8, the bag of the second embodiment of theinvention comprises a cover section 304 and a bag section 314. The coversection 304 and the bag section 314 are most preferably of substantiallythe same width, although in the illustrated embodiment, the coversection 304 is longer than the bag section 314. The cover section 304comprises first and second walls 310, 312 and the bag section 314comprises third and fourth walls 316, 318. The end 328 of the bagportion 314 is open (i.e. the third and fourth walls 316, 318 are notjoined together) to allow the bag portion 314 to be filled. At the sides320 and base 326 of the bag portion 314 the third and fourth walls 316,318 are permanently joined together, preferably by means of heatwelding, as indicated in regions 320A and 326A respectively. In regions320A at the sides of the bag 302 the respective first and second walls310, 312 are separably attached to the underlying bag portion 314.Similarly, at the upper end 328 of the bag 302, the first and secondwalls 310, 312 are separably attached to the underlying bag portion 314in region 328A, extending across the whole width of the bag 302. Inregions 320B and 322A the first and second walls 310, 312 are attachedto one another, preferably separably. In region 326A the first andsecond walls 310, 312 may be, but need not be, separably attached to thebag portion 314. In these regions 320A, 320B, 322A, 328A the first andsecond walls 310, 312 are preferably attached by heat welds.

The bag portion 314 is shown in FIGS. 6 and 7 as comprising a third wall316 which is shorter than fourth wall 318. The edge of the third wall316 is indicated at 316‡. However, the third and fourth walls 316, 318could be the same length, as indicated in FIG. 8.

In FIGS. 6 and 7, a closure flap 334 overlies the upper portion of thethird wall 316 and is attached to the third wall 316 by means of a bandor line or peelable adhesive 338. The closure flap 334 is in effect anextension of third wall 316 and is separably attached to first wall 310in region 328A. The closure flap includes a line of weakness 340 (and acorresponding line of weakness at the opposite side, not shown) alongwhich the closure flap 334 can be torn to expose the mouth 332 definedby upper edge 316‡ of third wall 316, whereby access is gained to thecontents of the bag portion 314.

The bag 302 includes a closeable region 342 between end 328 and themouth 332 (but not including the mouth 332). In closeable region 342,the third and fourth walls 316, 318 are, in use of the bag, sealedclosed after filling of the bag portion 314 with its desired contents.This is most preferably achieved by means of heat sealing. The closeableregion 342 is functionally the same as closeable region 42 of the firstembodiment of the invention.

For the avoidance of doubt, in FIG. 6, area W shows the complete bagincluding the first wall 310, in area X the first wall 310 is cut awayrevealing the closure flap 334, in area Y the closure flap is cut awayrevealing the third wall 316 and the fourth wall 318 and in area Z thethird wall is cut away revealing the second wall 312.

As mentioned above, the first and second walls 310, 312 of the coverportion 304 are separably attached to the bag portion 314, so as toenclose the bag portion. In the most preferred variations of theinvention, the separability is achieved by providing a treated area ortreated areas 344 which interfere with the strength of the union(preferably a heat seal) between the respective first and second walls310, 312 and the third and fourth walls 316, 318 or closure flap 334.The treated areas 344 are most preferably provided in the same way asthe treated areas 44 according to the first aspect of the invention.Thus the treated areas are preferably coated or printed areas. Forexample, printed regions may be provided on the third and fourth walls316, 318 and the closure flap 334 in areas corresponding to (butpreferably of somewhat greater extent than) regions 320A and 328A,together with an area corresponding to the closable region 342 and,optionally, areas corresponding to areas 320B and 326A. In other words,the treated areas 344 are provided in only those regions where the firstand second walls 310, 312 are attached to the third and fourth walls316, 318 and to the closure flap 334.

It is, however, more expedient in terms of the manufacture of the bags,and much preferred, to provide the treated area 344 across the whole ofthe inner surfaces of the first and second walls 310, 312 (that is,across the whole of the surfaces of the first and second walls 310, 312which oppose the bag portion 314). This means that, during manufactureof the bags and subsequently during heat sealing of the closeable regionthere is no uncertainty as to whether the heat sealing which joins thevarious walls together is, or is not, in a treated area 344. Of course,a treated area 344 is never formed on the internal surfaces of the thirdand fourth walls 316, 318 which define the interior of the bag portion.Most preferably, where the first and second walls 310, 312 are formedfrom a transparent material, the treated areas, especially printedareas, are also substantially transparent.

In a preferred form of the bags of this embodiment of the invention, thearea 328A, preferably the areas 320A and optionally the areas 320B and322A may, during manufacture be made somewhat wider than finallyrequired. These areas may then be trimmed, such as with an automaticknife or other cutting device to remove a small excess of material. Thisthen ensures that the bond between the various walls and between thewalls and the closure flap(s) in these regions extends right to the veryedge of the bag. This ensures that no crevices, recesses, channels orthe like are left which might harbour foreign bodies or infectiousagents (bacteria etc.) which could contaminate the contents of the bagportion 314. This is of especial importance in region 328A where thefirst wall 310, is joined respectively to the closure flap 334 (FIG. 7)or third wall 316 (FIG. 8) and the second wall 312 is joined to thefourth wall 318, as these regions are directly exposed to the product asit is being filled into the bag portion 318.

A variation of the bag of this second aspect of the invention is shownin FIG. 8 in which features corresponding or similar to those of FIG. 7are given like reference numbers and features which differ are givenreference numbers with the prefix “4”. In FIG. 8, an additional closureflap 434 is provided on an outer wall (first wall 310 or second wall312) of the bag 302. This construction is especially desirable where, asindicated in the preceding paragraph, the edges of the bag have beentrimmed during manufacture so that the bond between the various wallsand closure flaps extends right to the edge of the bag 302, mostespecially at end 328. Because the various walls and closure flap(s) arebonded right to the edge of the bag 302, it may be difficult for a userto obtain purchase or grip on one of the first or second walls 310, 312in order to separate the walls 310, 312 from the bag portion 314. Theadditional closure flap 434 allows such purchase or grip easily to beprovided in that, on tearing or peeling back of the tearable or peelableportion of the closure flap 434, the user has a substrate to grip whilepulling the respective first and second walls 310, 312 away from oneanother to separate them from the bag section 314. In a furtherpreferred variation, the wall lying below the closure flap 434 (firstwall 310 or second wall 312) may be provided with a mouth 442 in theform of a slit, or more preferably, in the form of a line of weaknesswhich may be ruptured as, or after, the closure flap 434 is peeled ortorn back. When the mouth 442 is opened the user is provided with anedge of the wall (310 or 312) which can be gripped directly for pullingthe walls 310, 312 away from one another.

In an alternative, but less preferred variation of the invention one orboth of the walls 310, 312 may be provided with a gripping tab, loop orthe like which a user can grasp for separating the cover section 304from the bag section 314.

As noted above, FIG. 8 shows a further variation in that the walls 316,318 of the bag section 314 are of equal length. The mouth 432 for accessto the interior of the bag section 314 is thus formed as a slit in wall316 which is closed by closure flap 334.

In use of the bags of this embodiment of the invention, the baf ispreferably manufactured by heat sealing the first and second wallsrespectively to the third and fourth walls at their edges. Because thefirst and second walls comprises a treated area across the whole oftheir inner faces, the heat sealing of the walls renders them separablewhen desired. The third and fourth walls are also heat sealed at theiredges, either contemporaneously with the heat sealing of the first andsecond walls to the third and fourth walls, or separately. Inmanufacture, no heat seal is formed between the third and fourth wallsat the top end 328 of the bag. The bag portion 314 is then filed withthe desired contents. A heat seal is applied in the closeable region tojoin the third and fourth walls together and so seal the contents withinthe bag section. This heat seal also further joins the first and secondwalls respectively to the third and fourth walls, the treated area ofthe first and second walls rendering this joint separable. The bag isthen stored and/or transported as required. When accessis required tothe contents of the bag portion 314, the first and second wall 310, 312are peeled away from the bag portion, with the assistance of the closureflap 434 if present. Access to the contents of the bag portion 314 isgained by peeling or tearing back the closure flap 334 and opening mouth332 through which the product Is dispensed.

Thus a particularly preferred plastic bag according to the secondembodiment of the invention comprises:

-   -   i) a bag section comprising third and fourth opposed walls        joined at their side and base edges and an open end by means of        which the bag section may be filled with contents;    -   ii) a cover section comprising first and second opposed walls        which are substantially co-extensive in width with the third and        fourth walls, arranged to enclose the bag section and attached        to the third and fourth walls at their side edges and upper        edge;    -   iii) a closeable mouth defined in a wall of the bag section for        access in use to the interior of the bag section;    -   iv) a closeable region, distinct from the mouth, including an        end portion of the cover section and an end portion of the bag        section proximate the open end of the bag section, within which        closeable region the bag section may be sealed closed after        filling;        wherein    -   (a) in the closeable region, the internal faces of the        respective first and second walls are attachable to the adjacent        external face of a wall of the bag section and    -   (b) the internal face of each of the first and second walls is        treated to provide alternating printed and non-printed areas        whereby the attachment of the first and second walls to the bag        section is such that the bag section is separable in use from        the cover section without compromising the seal of the bag        section in the closeable region.

The bag section may comprise a closure flap covering a mouth, the mouthproviding access to the interior of the bag section. In this case, oneof the first and second walls is attached to an outer surface of theclosure flap. Part of the closure may also lie in the closable region.

In another variation of both the first and second embodiments of theinvention, the third and/or fourth walls may be provided with aplurality of small holes 360 (FIG. 6), i.e. pin-holes of diameter notmore than about 1 mm, and preferably substantially less. These holes areprovided to allow air to escape from the interior of the bag section.The size and number of the holes is selected so that the air escapesgradually into the space between the third and fourth walls (and wherepresent, the closure flap) and the first and second walls. The air thenseeps or gradually escapes out of that space to the exterior. In thisway, air is not retained in the bags of the invention when the filledbags are stacked such as on a pallet. The product contained in the bagis of course retained in the bag and does not substantially pass throughthe pin-holes. By allowing the air to escape, the filled bags can bestacked more stably and are less vulnerable to bursting under thepressure generated by bags higher up a stack.

In accordance with this aspect of the invention there is provided aplastic bag comprising:

-   -   i) an inner bag portion defined by third and fourth walls joined        at their edges and base and having an open upper end;    -   ii) a cover portion enclosing the bag portion defined by first        and second walls joined at their edges and base, and    -   iii) at least one region in which the cover portion is joined to        the bag portion the third and/or fourth wall further comprising        a plurality of pin-holes by means of which air can gradually        escape from the bag portion when filled with contents into the        space between the cover portion and the bag portion.

Preferably the cover portion and bag portion are separably joined to oneanother. In this respect, preferably at least one of the walls, morepreferably the first and second walls include a treated region asdiscussed and defined above. Preferably also the bag of this aspect ofthe invention comprises a closure portion of the type defined anddescribed above.

1. A plastic bag comprising: i) a cover section comprising first andsecond opposed walls; ii) a bag section comprising third and fourthopposed walls joined at their side and base edges and an open end bymeans of which the bag section may be filled with contents, the firstand second walls being arranged to enclose the bag section; iii) acloseable mouth defined in a wall of the bag section for access in useto the interior of the bag section; iv) a closeable region, distinctfrom the mouth, including an end portion of the cover section and an endportion of the bag section proximate the open end of the bag section,within which closeable region the bag section may be sealed closed afterfilling; wherein, in the closeable region, an internal face of at leastone of the respective first and second walls is attached and/orattachable to an adjacent external face of a wall of the bag section,the attachment being such that the bag section is separable in use fromthe cover section without compromising the seal of the bag section inthe closeable region.
 2. A plastic bag as claimed in claim 1 wherein theopen end of the bag section may operatively be sealed after filling byheat sealing the bag section walls together in the closeable region. 3.A plastic bag as claimed in claim 1 wherein, for attachment of the coversection to the bag section in said closeable region, an internal face ofat least one of the respective first and second walls of the coversection is attachable to at least one external face of a bag sectionwall by heat sealing in the closeable region.
 4. A plastic bag asclaimed in claim 3 wherein at least one member selected from the groupcomprising the internal faces of the first and second walls and therespective external faces of the bag section walls comprises a firsttreated area in the closeable region, said first treated area beingeffective to limit the strength of the heat seal between the coversection and bag section.
 5. A plastic bag as claimed in claim 4 whereinsaid first treated area comprises printed areas, the printed areas beingresistant to heat sealing.
 6. A plastic bag as claimed in claim 1wherein the first and second walls are also separably attachedrespectively to the bag section walls in areas other than said closeableregion.
 7. A plastic bag as claimed in claim 6 wherein the first andsecond walls are removeably heat sealed respectively to the bag sectionwalls in said separably attached areas.
 8. A plastic bag as claimed inclaim 1 wherein at least one of the first wall and the adjacent bagsection wall and/or at least one of the second wall and the adjacent bagsection wall comprises a second treated area, said second treated areabeing effective to limit the strength of the heat seal betweenrespectively the first and third and the second and fourth walls in saidseparably attached areas.
 9. A plastic bag as claimed in claim 8 whereinsaid second treated area comprises printed areas, the printed areasbeing resistant to heat sealing.
 10. A plastic bag as claimed in claim3, wherein said first treated area extends across the whole innersurface of the first and/or second wall.
 11. A plastic bag as claimed inclaim 10 wherein the first and second walls are also separably attachedrespectively to the bag section walls in areas other than said closeableregion.
 12. A plastic bag as claimed in claim 11 wherein the first andsecond walls are removeably heat sealed respectively to the bag sectionwalls in said separably attached areas.
 13. A plastic bag as claimed inclaim 5 comprising, in a said treated area, alternate printed andnon-printed areas.
 14. A plastic bag as claimed in claim 13 wherein thearea of the printed areas is greater than the area of the non-printedareas.
 15. A plastic bag as claimed in claim 13 wherein the printed andnon-printed areas alternate to define stripes across the closeableregion and/or across the separably attached areas.
 16. A plastic bag asclaimed in claim 13 wherein the non-printed areas have a width of notmore than about 2 mm.
 17. A plastic bag as claimed in claim 13 whereinthe printed areas have a width of not more than about 10 mm.
 18. Aplastic bag as claimed in claim 4 wherein the treated area comprises anembossed area of one or more of the walls.
 19. A plastic bag as claimedin claim 1 wherein the cover section is longer than the bag section suchthat the cover section extends beyond the base end of the bag section,the first and second walls being joined to each other in said lengthwiseextending portion.
 20. A plastic bag as claimed in claim 1 wherein thewidth of the cover section is greater than the width of the bag sectionsuch that the cover section extends beyond the side edges of the bagsection, the first and second walls being joined to each other in saidwidthwise extending portion.
 21. A plastic bag as claimed in claim 6wherein the width of the cover section is greater than the width of thebag section such that the cover section extends beyond the side edges ofthe bag section, the first and second walls being joined to each otherin said widthwise extending portion.
 22. A plastic bag as claimed inclaim 1 further comprising: a first closure flap overlying and closingsaid mouth defined in a wall of said bag section said first closure flapincluding a first attached region which is peelably attached to said bagsection wall such that at least a portion of said first closure flap maybe peeled away from said bag section wall across the peelably attachedregion to reveal the mouth, and, optionally, a second attached regionspaced from the peelably attached region in which second region saidfirst closure flap is also attached to said bag section wall.
 23. Aplastic bag as claimed in claim 1 comprising: a first closure flapoverlying and closing said mouth defined in a wall of said bag sectionsaid first closure flap including a first region which is attached to asaid bag section wall, said first closure flap including at least oneline of weakness defining a tearable portion of said first closure flapwithin which tearable portion said first closure flap is not attached tothe bag section wall and which tearable portion can be opened by tearingalong the line of weakness to reveal the mouth; and, optionally, asecond attached region spaced from the tearable portion in which secondregion said first closure flap is also attached to said bag sectionwall.
 24. A plastic bag as claimed in claim 22 wherein the first closureflap extends into the closeable region.
 25. A bag as claimed in claim 24further comprising a closure flap; wherein, for attachment of the coversection to the bag section in said closeable region, an internal face ofat least one of the respective first and second walls of the coversection is attachable to at least one external face of a bag sectionwall by heat sealing in the closeable region; wherein at least onemember selected from the group comprising the internal faces of thefirst and second walls and the respective external faces of the bagsection walls comprises a first treated area in the closeable region,said first treated area being effective to limit the strength of theheat seal between the cover section and bag section; wherein the firstclosure flap is overlying and closing said mouth defined in a wall ofsaid bat section said first closure flap including a first attachedregion which is peelably attached to said bag section wall such that atleast a portion of said first closure flap may be peeled away from saidbag section wall across the peelably attached region to reveal themouth, and, optionally, a second attached region spaced from thepeelably attached region in which second region said first closure flapis also attached to said bag section wall; and wherein a first treatedarea is formed on the first closure flap instead of a treated area ofthe bag section.
 26. A plastic bag according to claim 1 wherein on orboth of the respective first and second walls of the cover sectionis/are adhered to the bag section proximate the open end of the bagsection.
 27. A plastic bag as claimed in claim 26 wherein the coversection is adhered to the bag section at marginal portions of thecloseable region.
 28. A plastic bag as claimed in claim 1 furthercomprising a second closeable mouth defined in the first or second wallof the cover section for access in use to the bag section.
 29. A plasticbag as claimed in claim 1 further comprising: a second closure flapincluding a first region which is peelably attached to said coversection wall such that at least a portion of the closure flap may bepeeled away from said cover section wall across the peelably attachedregion and a second attached region spaced from the peelably attachedregion in which second region the second closure flap is also attachedto said cover section wall.
 30. A plastic bag as claimed in claim 1further comprising: a second closure flap including a first region whichis attached to said cover section wall, the second closure flapincluding at least one line of weakness defining a tearable portion ofthe closure flap within which tearable portion the closure flap is notattached to said cover section wall and which tearable portion can beopened by tearing along the line of weakness and a second attachedregion spaced from the tearable portion in which second region thesecond closure flap is also attached to said cover section wall.
 31. Aplastic bag as claimed in claim 29 wherein the second closure flap isarranged to cover the second mouth.
 32. A plastic bag as claimed inclaim 1 further comprising gripping means formed in or on, or attachedto the first or second walls, to facilitate gripping of said walls onseparation of the cover section from the bag section.
 33. A method ofhandling a flowable product comprising: i) providing a bag as claimed inclaim 1; ii) filling the bag section with the flowable product throughthe open end of the bag; and iii) applying heat sealing means to thecloseable region thereby to heat seal the bag section walls together tosealingly close the bag section and to heat seal the first and/or secondwalls to the bag section walls to separably attach cover section and bagsection together.
 34. A method as claimed in claim 33 furthercomprising: iv) separating the cover section from the bag section in thecloseable region; v) if necessary, separating the cover section from thebag section outside the closeable region and vi) withdrawing the bagsection from the cover section.
 35. A plastic bag comprising: i) a coversection comprising first and second opposed walls; ii) a productcontaining bag section comprising third and fourth opposed walls joinedat their side and base edges, the first and second walls being arrangedto enclose the bag section; iii) a closeable mouth defined in a wall ofthe bag section for access in use to the interior of the bag section;iv) a sealing region, distinct from the mouth, including an end portionof the cover section and an end portion of the bag section within whichsealing region the bag section is sealed closed after filling bagsection with product; wherein, in the sealing region, an internal faceof at least one of the respective first and second walls is attached toan adjacent external face of a wall of the bag section, the attachmentbeing such that the bag section is separable in use from the coversection without compromising the seal of the bag section in the sealingregion.
 36. A plastic bag as claimed in claim 35 wherein, within thesealing region the respective first and second walls of the coversection are attached to at least one of the external faces of therespective bag section walls of the bag section by means of a heat sealformed contemporaneously with the heat seal which seals the bag sectionwalls.
 37. A plastic bag as claimed in claim 36 wherein at least one ofthe internal faces of the first and second walls and the external facesof the bag section walls comprises a treated area in the sealing region,the treated area being effective to limit the strength of the heat sealbetween the cover section and bag section.
 38. A plastic bag as claimedin claim 35 further comprising: a first closure flap overlying andclosing said mouth defined in a wall of said bag section said firstclosure flap including a first attached region which is peelablyattached to said bag section wall such that at least a portion of saidfirst closure flap may be peeled away from said bag section wall acrossthe peelably attached region to reveal the mouth, and, optionally, asecond attached region spaced from the peelably attached region in whichsecond region said first closure flap is also attached to said bagsection wall.
 39. A plastic bag as claimed in claim 35 comprising: afirst closure flap overlying and closing said mouth defined in a wall ofsaid bag section said first closure flap including a first region whichis attached to a said bag section wall, said first closure flapincluding at least one line of weakness defining a tearable portion ofsaid first closure flap within which tearable portion said first closureflap is not attached to the bag section wall and which tearable portioncan be opened by tearing along the line of weakness to reveal the mouth;and, optionally, a second attached region spaced from the tearableportion in which second region said first closure flap is also attachedto said bag section wall.
 40. A plastic bag as claimed in claim 38wherein the first closure flap extends into the closeable region.
 41. Abag as claimed in claim 40 wherein at least one of the internal faces ofthe first and second walls and the external faces of the bag sectionwalls comprises a treated area in the sealing region, the treated areabeing effective to limit the strength of the heat seal between the coversection and bag section; and further comprising: a first closure flapoverlying and closing said mouth defined in a wall of said bag sectionsaid first closure flap including a first attached region which ispeelably attached to said bag section wall such that at least a portionof said first closure flap may be peeled away from said bag section wallacross the peelably attached region to reveal the mouth, and,optionally, a second attached region spaced from the peelably attachedregion in which second region said first closure flap is also attachedto said bag section wall; wherein a first treated area is formed on thefirst closure flap instead of a treated area of the bag section. 42.(canceled)